I am not sure, to be honest. I also tried 8080 (external) to 80 (internal) to no avail. I'm a Comcast/Xfinity customer.
Edit: Right now I have it set up for:
Static IP for device.
Port 8080 External to 80 Internal
Rebooted router and while it all works internally just fine I can't see it...
I, too, have a Heatermeter and Google Wifi and I'm running into issues with port forwarding.
I can see the HM just fine locally in my browser, but remote connections do not seem to work. I created a static IP for the device, then forwarded the port (80>80 and X>80) and tried rebooting the...